import java.util.Scanner;

/**
Some more examples for String processing.
*/
public class StringProcess
{
  /** Problem: Given a string with lots of words separated by spaces,
    * return the nth word in the string. */
   public static void main(String[] args)
   {
      String doc="Four score and seven years ago"; 
      // for loop n-1 times to find space before the nth word
      int pos=-1, n=6;
      for (int i=0;i<n-1;i++) {
          pos = doc.indexOf(' ',pos+1);
          if (pos==-1) {
             System.out.println("There are fewer than " + n + " words in" 
                                + " the string being searched. ");
             System.exit(0);
          }
      }
      int endPos=doc.indexOf(' ', pos+1);
      if(endPos==-1)
          endPos=doc.length();
      System.out.println("The " + n + " word is: " + 
                         doc.substring(pos+1, endPos));
      if (isValid("AB12"))
        System.out.println("AB12 is valid");
      if (!isValid("aac0"))
        System.out.println("aac0 is not valid");
   }
   
   /*This method will verify a productID. The format is:
    * XX00 where X is an uppercase letter and 0 is any digit.
    */
   public static boolean isValid(String prodID) {
    
     // has to be 4 characters long
     if (prodID.length()!=4)
         return false;
     // first 2 must be uppercase letters
     // last 2 must be digits
     if (Character.isLetter(prodID.charAt(0)) && 
         Character.isUpperCase(prodID.charAt(0)) &&
         Character.isLetter(prodID.charAt(1)) && 
         Character.isUpperCase(prodID.charAt(1)) &&
         Character.isDigit(prodID.charAt(2)) && 
         Character.isDigit(prodID.charAt(3)))
       
         return true;
     
     return false;
     
     // a different way of doing the same thing, just using loops
     // checks first 2 characters
     for (int i=0;i<2;i++)
       if (!(Character.isLetter(prodID.charAt(i)) && 
         Character.isUpperCase(prodID.charAt(i))))
              return false;
     for (int i=2; i<4; i++)
       if (!Character.isDigit(prodID.charAt(i)))
             return false;
     return true;
   }
   
   
   
   
   
   
}